Image-formation on electro-photographic material



IMAGE-FORMATION ON ELECTROPHOTOGRAPHIC MATERIAL Filed May 21, 1963 R. M.GOLD Sept. 14, 1965 g Sheets-Sheet 1 FIG.

FORMING A LATENT IMAGE IN AN ELECTROPHOTOGRAPHIC MATERIAL BY MEANS OFPRESSURE DEVELOPING THE LATENT IMAGE RENDER IT VISIBLE FIG.2

CHARGING ELECTROSTATICALLY (OPTIGNAL) EXPOSING UNIFORMLY (OPTIONAL) IFORMING LATENT IMAGE BY PRESSURE (REQUIRED) l Y' V L CHARGINGELECTROSTATICALLY IQPTIQNAL) I I REVERSE CHARGING (OPTIONAL) I L JEXPOSING UNIFORMLY DEVELOPING LATENT IMAGE (REQUIRED) Em a Sept. 14,1965 R. M. GOLD IMAGE-FORMATION ON ELECTROPHOTOGRAPHIC MATERIAL FiledMay 21, 1963 2 Sheets-Sheet 2 FIG. 3A

PHOTOCONDUCTIVE LAYER 32 SUPPORT 3| ELECTROPHOTOGRAPHIC MATERIA L 3 OFIG. 3B

LATENT IMAGE AREA 33 PHOTOCONDUCT IVE LAYER 32 SUPPORT 3|ELECTROPHOTOGRAPHIC MATERIAL 3O FIG.3C

TONER 34 LATENT IMAGE AREA 33 PHOTOCONDUCTIVE LAYER 32 SUPPORT 3| ELECTROPHOTOGRAPHIC MATERIAL 3O FIG. 3D

LATENT IMAGE AREA 33 TONER 35 ELECTROPHOTOGRAPHIC MATERIAL 3O INVENTORROBERT M. GOLD ATTOR N EY United States Patent 3,206,600 IMAGE-FORMATIONON ELECTRO. PHOTOGRAPHIC MATERIAL Robert M. Gold, Brooklyn, N.Y.,assignor to Keulfel & Esser Company, Hobolren, Ni, a corporation of NewJersey Filed May 21, 1963, Ser. No. 282,121 14 @laims. (Cl. 250--65) Thepresent invention relates to image formation and refers moreparticularly to image formation on electrophotographic materials bymeans of pressure with and Without electrostatic charging.

The electrophotographic method for the production of images comprisesthe sequential operations of charging, exposing, developing, and fixingan electrophotographic material such as a support coated with a layer ofphotoconductive material. It has now been found that latent imageformation can be obtained by means of pressure with and withoutcharging. The particular se quence of charging and exposing is thusobviated. Other limitations are also avoided.

One object of the present invention is to provide a method of makingimages on electrophotographic materials which avoids the disadvantagesof the prior art.

Another object is to provide a method of producing an image on aelectrophotographic material by means of pressure with and withoutelectrostatic charging.

Another object is to provide a method of making reproductions of graphicintelligence and the like.

Another object is to provide a method of making latent images onelectrophotographic materials by means of pressure with and Withoutelectrostatic charging, said latent images being developable byelectrophotographic developers.

Other objects will become apparent during the course of thespecification.

In the drawing:

FIGURE 1 is a flow sheet showing the essential steps of the presentinvention;

FIGURE 2 is a flow sheet showing the sequence of optional steps in thepractice of the present invention;

FIGURE 3A shows side sectional views of an electrophotographic material,313 a latent image-bearing electrophotographic material, 3C a positivelydeveloped electrophotographic material, and 3D a negatively developedelectrophotographic material of the present invention.

The present invention will appear more clearly from the followingdetailed description when taken in connection with the accompanyingdrawing showing, by way of example, preferred embodiments of the presentinvention.

It has been found in the present invention that a suitableelectrophotographic material is affected by the imagewise application ofpressure with and without charging so that the affected areas aredistinguishably diiferent from the unaffected areas. This difference maybe developed to form a visible image. For example in FIG- URE 1 apressure pattern applied to a suitable electrophotographic materialproduces an invisible pressure pattern affected-area which differs fromthe unaifected areas of the material and which is developable to producea visible pattern. Development is improved by charging the material asin FIGURE 2 to utilize the difference in charge acceptance or retentionbetween the two areas. Pressure applied before charging as in steps 2Dand 2E results in retention of the charge in the pressure-affected areasfor a longer time than in the pressure unaffected areas, and the reverseis true when the pressure pattern is applied after charging as in steps2A and 2B. Charg ing increases the difference between the two areas butdevelopment may be accomplished without it.

Pressure may also be applied to the electrophotographic material afterit has been uniformly exposed to actinic radiation as in steps 2C and2D. By varying the sequence of pressure application as in steps 2D and26, many different methods may be obtained.

Various combinations of pressure may be used to obtain differentresults. Halftones may be obtained by a pressure pattern from a silkscreen or similar material. Post-pressure exposure to electrostaticcharges, and uniform exposure to actinic radiation produce varyingeffects depending upon their order. In each case development produces avisible image.

Development may be accomplished by using electroscopic toners like thoseemployed in the electrophotographic art. Two examples are a carrierlesselectroscopic powder material and an insulating liquid containing suchelectroscopic material. The electroscopic powder may also be intimatelymixed with suitable carrier particles for enhancing the electroscopiccharge by triboelectric means and for use with the well-known magneticbrush technique or the cascading technique. These electroscopic tonersare applied to the latent image-bearing material as in step 2H and arethen fixed as in step 21 by fusing.

The toners may be electroscopically positive or negative and they may beused in the form of particulate solids, liquid dispersions, orsolutions. The toners are generally dark-colored in order to contrastwith the electrophotographic material. Toners which take a positivecharge include powdered asphaltum with glass beads as the carrier. Theasphaltum powder takes a positive charge with respect to the glassbeads. Toners with a negative charge on the particles include carbonblack suspended in heptane containing 0.01% lecithin. The carbon blackis negative with respect to the heptane. Other toners include those withmagnetizable carrier particles. Toners comprising thermoplasticmaterials adhere well when heat-fused to the material.

The developing and the fixing operations may be combined by means of aliquid developer comprising a liquid medium, toner, and binder.Development occurs when the liquid developer is applied to a layerbearing a developable latent image and the toner selectively adheres tothe layer to define the image. Fixing occurs when the liquid medium isremoved and the binder permanently adheres the toner to the layer.

Fixing may also be accomplished by solvent fusing or by transparentadhesive film applied to the material over the toner.

The quality of the developed image is generally improved by treatmentsto intensify or de-intensify the developable diiference between thelatent image areas and the non-image areas before developing and fixing.Some of these treatments are charging, reverse-charging, exposinguniformly to ultraviolet radiation, heating, and combinations of thesetreatments.

Electrophotographic materials suitable for the present invention arephotoconductor-coated supports such as paper, film and the like. Thematerials may also be self-sustaining layers. Photoconductors such aszinc oxide, lead titanate, cadmium sulfide, and polyvinyl carbazole maybe used. Insulating binders such as silicone resins andstyrene-butadiene polymers may be used.

One simple means of charging the surface of the material is by use of aconductive rubber roller raised to a potential of 1000 to 1500 volts andused as a pinch roller cooperating with a grounded plate or acooperating roller. A simple source of voltage may be a series ofbatteries producing 1500 volts. Another means of charging is by coronadischarge.

The invention is further illustrated by the following examples.

3 Examples (1) An electrophotographic material 30 as in FIGURE 3Acomprising a photoconductive layer 32 on a support 31 Was insertedbehind a sheet of conventional bond typing paper into a typewriter. Thelayer comprised at least one of the following photoconductors: zincoxide, cadmium sulfide, lead titanate and polyvinyl carbazole. The bondpaper was typed upon and a pressure-created latent image 33 in FIGURE 3Bwas simultaneously formed in the electrophotographic material. This wasgiven a negative electrostatic charge by means of a corona discharge andtreated with a positive toner 34 in FIGURE 3C to produce a visiblepositive image of the typing on the electroprotographic material. Thedeveloped positive image was then fixed by heating. A copy was thusproduced without the use of carbon paper.

The same results were obtained with a pencil and ordinary writingpressure in place of the typewriter key.

(2) Example 1 was repeated with a negative toner 35 as in FIGURE 3D toproduce a white-on-black or negative copy.

(3) Example 1 was repeated with positive charging instead of negativecharging. The use of a positive toner produced a white-on-black print ornegative copy.

(4) Example 1 was repeated using positive charging instead of negativecharging. Development with a negative toner produced a black-on-whiteprint or positive.

(5) The electrophotographic material of Example 1 was first given anegative electrostatic charge and then subjected to a pressure pattern.Development with a positive toner produced a white-on-black print ornegative. The toner was fixed as in Example 1.

(6) Example 5 was repeated with a negative toner instead of a positivetoner to produce a black-on-White positive print.

(7) Example 5 was repeated with positive charging in stead of negativecharging. Development with a positive toner produced a black-on-whitepositive print.

(8) Example 5 was repeated with positive charging. Development with anegative toner produced a white-onblack negative print.

(9) Example 1 was repeated but after charging, the electrophotographicmaterial was uniformly exposed to ultraviolet light as in step 2G for afew seconds to reduce the intensity of the charge and to give a moreaccurate reproduction. The material was developed and fixed as inExample 1.

(10) Example 2 was repeated but after charging, the material wasuniformly exposed to ultraviolet light for a few seconds to reduce theintensity of the charge and to give a more accurate reproduction. Thematerial was developed and fixed as in Example 2.

(11) Example 3 was repeated but after charging, the material wasuniformly exposed to ultraviolet light for a few seconds to reduce theintensity of the charge and to give a more accurate reproduction. Thematerial was developed and fixed as in Example 3.

(12) Example 4 was repeated but after charging, the material wasuniformly exposed to ultraviolet light for a few seconds to reduce theintensity of the charge and to give a more accurate reproduction. Thematerial was developed and fixed as in Example 4.

(13) Example 5 was repeated but after charging, the material wasuniformly exposed to ultraviolet light for a few seconds to reduce theintensity of the charge and to give a more accurate reproduction. Thematerial was developed and fixed as in Example 5.

(14) Example 6 was repeated but after charging, the material wasuniformly exposed to ultraviolet light for a few seconds to reduce theintensity of the charge and to give more accurate reproduction. Thematerial was developed and fixed as in Example 6.

(15) Example 7 was repeated but after charging, the material wasuniformly exposed to ultraviolet light for a few seconds to reduce theintensity of the charge and to give a more accurate reproduction. Thematerial was developed and fixed as in Example 7.

(16) Example 8 was repeated but after charging, the material wasuniformly exposed to ultraviolet light for a few seconds to reduce theintensity of the charge and to give a more accurate reproduction. Thematerial was developed and fixed as in Example 8.

(17) Example 1 was repeated but after charging the material, it wasreverse charged with the opposite polarity as in step 2F to reduce theintensity of the initial charge and to give a more accuratereproduction. The material was developed and fixed as in Example 1.

(18) Example 2 was repeated but after charging the material, it wasreverse charged with the opposite polarity to reduce the intensity ofthe initial charge and to give a more accurate reproduction. Thematerial was d veloped and fixed as in Example 2.

(19) Example 3 was repeated but after charging the material, it wasreverse charged with the oppoiste polarity to reduce the intensity ofthe initial charge and to give a more accurate reproduction. Thematerial was developed and fixed as in Example 3.

(20) Example 4 was repeated but after charging the material, it wasreverse charged with the opposite polarity to reduce the intensity ofthe initial charge and to give a more accurate reproduction. Thematerial was developed and fixed as in Example 4.

(21) Example 5 was repeated but after charging the material, it wasreverse charged with the opposite polarity to reduce the intensity ofthe initial charge and to give a more accurate reproduction. Thematerial was developed and fixed as in Example 5.

(22) Example 6 was repeated but after charging the material, it wasreverse charged with the opposite polarity to reduce the intensity ofthe initial charge and to give a more accurate reproduction. Thematerial was developed and fixed as in Example 6.

(23) Example 7 was repeated but after charging the material, it wasreverse charged with the opposite polarity to reduce the intensity ofthe initial charge and to give a more accurate reproduction. Thematerial was developed and fixed as in Example 7.

(24) Example 8 was repeated but after charging the material, it wasreverse charged with the opposite polarity to reduce the intensity ofthe initial charge and to give a more accurate reproduction. Thematerial was developed and fixed as in Example 8.

(25) Five sheets of zinc oxide coated electrophotographic paper wereinserted into a typewriter with a cover sheet of conventional bondtyping paper. The usual typewriter ribbon copy was made on the coversheet with corresponding pressure patterns on the copy pages. Thereafterthe plurality of sheets of Zinc oxide and resin coated copy paper wereeach subjected to a corona discharge to produce an electrostatic chargeon the zinc oxide coated surface of each sheet of electrophotographicpaper. These sheets were then uniformly subjected to actinic light overtheir entire surface. An electroscopic toner was then applied to eachsheet, and a clear image of the typing was developed. The toner was thenfixed by heating to produce a permanent copy on each sheet. This methodavoided the use of carbon paper in making multiple copies and thusavoided the objectionable smudged areas which frequently occur in theuse of conventional carbon paper in making multiple copies. All copieswere black-onwhite positives.

(26) The zinc oxide surface of an electrophotographic paper wassubjected to pressure through a x 100 mesh silk screen between fiatsurfaces to form a fine pressure-affected grid pattern on the coating.The paper was subsequently electrostatically charged by a coronadischarge and exposed through a positive transparency to actinic lightto form a latent image. A thermoplastic particulate toner was applieddirectly to the latent electrostatic image. It adhered to a greaterextent in the pressure affected areas of the image area to produce ahalf tone black-on-white copy of the image.

(27) A sheet of electrophotographic paper was placed under a bond papersheet in a typewriter. Pressure from the typewriter key produced alatent image on the sheet of electrophotographic paper simultaneouslywith the character impression on the bond paper sheet. Development ofthe latent image on the electrophotographic sheet without charging withpositive toner produced a blackon-white image which was fixed byconventional means.

(28) Example 27 was repeated with a negative toner instead of a positivetoner to produce a white-on-black image.

(29) Latent images were produced in a electrophotographic sheet placedunder a bond paper sheet which was written upon with a pencil usingordinary pressure. The latent images were developed by using a positivetoner with a magnetic brush. After sufiicient brushing a blackon-whiteimage was produced. This was fixed in a conventional manner.

(30) Example 29 was repeated with a negative toner instead of a positivetoner to produce a white-on-black image which was fixed in aconventional manner.

(31) Finger prints were produced on electrophotographic material bycharging the surface of the paper contacting the surface with thefingertips, and developing with a suitable toner. The developed imagewas fixed to produce a permanent record. A black-on-white print wasproduced with a negative toner.

It is apparent that the described examples are capable of manyvariations and modifications within the scope of the present invention.All such variations and modifications are to be included within thescope of the present invention.

What is claimed is:

1. A method of making an image on a single photoconductiveelectrophotographic layer, which comprises the steps of:

pressure-imaging a pattern on said layer to form a relatively permanent,latent, developable image surrounded by non-image areas; and

developing said latent image by applying electroscopic toner whichcontrasts with the layer and which selectively adheres to the imageareas of said layer to render the latent image visible.

2. A method of making an image on a single photoconductiveelectrophotographic layer, which comprises the steps of pressure-imaginga pattern on said layer to form a relatively permanent, latent,developable image surrounded by non-image areas; and

developing said latent image by applying electroscopic toner whichcontrasts with the layer and which selectively adheres to the non-imageareas of said layer to render the latent image visible.

3. A method of making an image on a single photoconductiveelectrophotographic layer, which comprises the steps of:

pressure-imaging a pattern on said layer to form a relatively permanent,latent, developable image surrounded by non-image areas;

charging said layer electrostatically with one polarity to produce acharge image corresponding to said latent image; and

developing said charge image by applying an electroscopic toner whichcontrasts with the layer and which selectively adheres to the imageareas of said layer to render the latent image visible.

4. A method of making an image on a single photoconductiveelectrophotographic layer, which comprises the steps of:

pressure-imaging a pattern on said layer to form a relatively permanent,latent, developable image surrounded by non-image areas;

charging said layer electrostatically with one polarity to produce acharge image corresponding to said latent image; and

developing said charge image by applying an electroscopic toner whichcontracts with the layer and which selectively adheres to the non-imageareas of said layer to render the latent image visible.

5. A method of making an image on a single photoconductiveelectrophotographic layer, which comprises the steps of:

pressure-imaging a pattern on said layer to form a relatively permanent,latent, developable image surrounded by non-image areas;

charging said layer electrostatically with one polarity to for-m acharge image corresponding to said latent image;

exposing said layer uniformly to ultraviolet radiation to reduce theintensity of the charge on said layer; and

developing said charge image on said layer by applying electroscopictoner which contrasts with the layer and which selectively adheres tothe image areas of said layer to render the latent image visible.

6. A method of making an image on a single photoconductiveelectrophotographic layer, which comprises the steps of:

pressure-imaging a pattern on said layer to form a relatively permanent,latent, developable image surrounded by non-image areas;

charging said layer electrostatically with one polarity to form a chargeimage corresponding to said latent image;

exposing said layer uniformly to ultraviolet radiation to reduce theintensity of the charge on said layer; and

developing said charge image on said layer by applying electroscopictoner which contrasts with the layer and which selectively adheres tothe non-image areas of said layer to render the latent image visible.

7. A method of making an image on a single photoconductiveelectrophotographic layer, which comprises the steps of:

pressure-imaging a pattern on said layer to form a relatively permanent,latent, developable image surrounded by non-image areas;

charging said layer electrostatically with one polarity to form a chargeimage corresponding to said latent image;

reverse-charging said layer with an electrostatic charge of oppositepolarity to reduce the intensity of the first charge; and

developing said charge image in said layer by applying electroscopictoner which contrasts with the layer and which selectively adheres tothe image areas of said layer to render the latent image visible.

8. A method of making an image on a single photoconductiveelectrophotographic layer, which comprises the steps of:

pressure-imaging a pattern on said layer to form a rela tivelypermanent, latent, developable image surrounded by non-image areas;

charging said layer electrostatically with one polarity to form a chargeimage corresponding to said latent image;

reverse-charging said layer with an electrostatic charge of oppositepolarity to reduce the intensity of the first charge; and

developing said charge image in said layer by applying electroscopictoner which contrasts with the layer and which selectively adheres tothe non-image areas of said layer to render the latent image visible.

9. A method of making an image on a single photoconductiveelectrophotographic layer, which comprises the steps of:

uniformly charging said layer electrostatically with one polarity;

pressure-imaging a pattern on said charge layer to form a relativelypermanent, latent, developable image surrounded by non-image areas; and

developing said latent image on said material by applying electroscopictoner which contrasts with the layer and which selectively adheres tothe image areas of said layer to render the latent image visible.

10. A method of making an image on a single protoconductiveelectroprotographic layer, which comprises the steps of:

uniformly charging said layer electrostatically with one polarity;

pressure-imaging a pattern on said charge layer to form a relativelypermanent, latent, developable image surrounded by non-image areas; and

developing said latent image on said material by applying electroscopictoner which contrasts with the layer and which selectively adheres tothe nonimage areas of said layer to render the latent image visible.

11. A method of making an image on a single photoconductiveelectrophotographic layer, which comprises the steps of:

uniformly charging said layer electrostatically with one polarity;

reverse-charging said layer with an electrostatic charge of oppositepolarity to reduce the intensity of the first charge;

pressure-imaging a pattern on said layer to form a relatively permanent,latent, developable image sur- 1 rounded by non-image areas; anddeveloping said image in said layer by applying electroscopic tonerwhich contrasts with the layer and which selectively adheres to theimage areas of said layer to render the latent image visible.

12. A method of making an image on a single photoconductiveelectrophotographic layer, which comprises the steps of:

uniformly charging said layer electrostatically with one polarity;

reverse-charging said layer with an electrostatic charge of oppositepolarity to reduce the intensity of the first charge;

pressure-imaging a pattern on said layer to form a relatively permanent,latent, developable image' surrounded by non-image areas; and

developing said image in said layer by applying electroscopic tonerwhich contrasts with the layer and which selectively adheres to thenon-image areas of said layer to render the latent image visible.

13. A method of making an image on a single photoconductiveelectrophotographic layer, which comprises the steps of:

uniformly charging said layer electrostatically with one polarity;exposing said layer uniformly to ultraviolet radiation to reduce theintensity of the charge on said layer;

pressure-imaging a pattern on said layer to form a relatively permanent,latent, developab-le image surrounded by non-image areas; and

developing said image on said layer by applying electro= scopic tonerwhich contrasts with the layer and which selectively adheres to theimage areas of said layer to render the latent image visible.

14. A method of making an image on a single photocon-ductiveelectrophotographic layer, which comprises the steps of:

uniformly charging said layer electrostatically with one polarity;exposing said layer uniformly to ultraviolet radiation to reduce theintensity of the charge on said layer;

pressure-imaging a pattern on said layer to form a relatively permanent,latent, developable image surrounded by non-image areas; and

developing said image on said layer by applying electroscopic tonerwhich contrasts with the layer and which selectively adheres to thenon-image areas of said layer to render the latent image visible.

References Cited by the Examiner UNITED STATES PATENTS 2,798,960 7/57Moncrieff-Yeates 250 2,914,403 11/59 Sugarman 250-65 X 3,095,301 6/63Kostelee Q 25065 X 3,108,894 10/63 Stowell 117--17.5 3,114,633 12/63Schlesinger 250-65 'X 3,121,007 2/64 Middleton 250--65 X 3,124,482 3/64Olden 117-l7.5 X 3,128,198 4/64 Dulmage et a1 117--17.5 3,134,849 5/64Frobach et al. 117-17.5 X

OTHER REFERENCES Cassiers: Electrothermographya New Electra-staticPrinting Technique, Photographic Science and Engineering, vol. 4, No. 4,July-August 1960, pp. 199 to 202.

Claus: Advances in Xerography, 1958-1962, Photographic Science andEngineering, vol. 7, No. 1, January- February 1963, pp. 5 to 14. 1

RALPH G. NILSON, Primary Examiner.

1. A METHOD OF MAKING AN IMAGE ON A SINGLE PHOTOCONDUCTIVEELECTROPHOTOGRAPHIC LAYER, WHICH COMPRISES THE STEPS OF:PRESSURE-IMAGING A PATTERN ON SAID LAYER TO FORM A RELATIVELY PERMANENT,LATENT, DEVELOPABLE IMAGE SURROUNDED BY NON-IMAGE AREAS; AND DEVELOPINGSAID LATENT IMAGE BY APPLYING ELECTROSCOPIC TONER WHICH CONTRAST WITHTHE LAYER AND WHICH SELECTIVELY ADHERES TO THE IMAGE AREAS OF AID LAYERTO RENDER THE LATENT IMAGE VISIBLE.